This invention relates to high energy density electric cells or batteries and more particularly to pressure-compensation for high energy density batteries. With the continuous development of high energy density battery systems, these electric cells or batteries are being used in applications that place ever greater demands on the electrical power output and discharge life of the battery. In other words, high energy density batteries are being used in hostile environments for which the batteries may not normally be suited. Examples of these applications include, but are not limited to, use in sonobuoys, mines, transponders, surveillance systems, and vehicles.
The high energy high density electric cell of the present invention is contained in a casing having a hermetically integral flexible mechanical pressure-compensation device, such as a bellows. The pressure-compensation device is provided on one end of the cell casing which is hollow and preferably made of a stainless steel material. The mechanical pressure-compensation device is preferably made of a similar material and makes use of the compressibility of the material contained inside the cell casing to effect internal pressure compensation. This material may comprise a liquid and/or vapor and/or gas phase and may, but does not need, to serve as the electrolyte and/or catholyte of the cell. The cell may also have a pressure-relief component such as a pressure-relief vent. This is dependent upon the specific application for which the cell or battery is intended. If a pressure-relief vent is used, it is preferably mounted in the bottom of the bellows. Further, the header assembly at the other end of the cell casing may have a glass-to-metal seal as the pressure-relief component. In this case, the pressure-relief vent may not be necessary. Instead, pressure-relief will take place through the header of the cell. Whether or not a pressure-relief component is included with the mechanical pressure-compensating device, it should be understood that the resultant cell container is an integral unit that retains hermeticity, which is especially important in a lithium cell system.